1. Field of the Invention
The invention relates to a cable connector to electrically connect cables to each other, and specifically to a coaxial connector with a structure capable of electrically connecting coaxial cables to each other without requiring any manual work when a connection system for transmitting radio-frequency power is built.
2. Description of the Related Art
In recent years, a growing number of processes of manufacturing electrical apparatuses have used radio-frequency power. In addition, there is a tendency that the frequency and magnitude of the power used for this purpose have become higher and higher. Transmission of radio-frequency power in such manufacturing processes needs transmission lines with the above-described coaxial structure to take advantage of the efficiency of the radio-frequency power transmission. Transmission lines of coaxial structure are connected to each other with special cable connectors called coaxial connectors. Coaxial connectors allow electrical connection between such coaxial cables, or between the coaxial cable to an electrical apparatus or a measurement instrument.
Meanwhile, a coaxial cable includes: a center conductor used for transmitting, for example, radio-frequency (RF) power or RF signals; an insulator layer (dielectric) provided around the center conductor; an outer conductor provided around the insulator; and a protective layer coating the outer conductor. Such coaxial cable has a rated characteristic impedance (e.g., 50Ω or 75Ω) for electric signal transmission.
Various fixing means have been proposed as methods allowing electrical connection between such coaxial cables by use of a coaxial connector. Some of the currently proposed means are screw-in fixing means, and such fixing means capable of one-touch connection as ball-locking mechanisms and bayonet-sleeve mechanisms (see, for example, Japanese Patent Application Publication No. 2006-147272, Japanese Utility Model Registration Application No. 2009-123591, U.S. Pat. No. 5,928,021).
However, the connection with connectors by those means described in Patent Literatures 1 to 3 require manual work, and hence is not preferable in view of safety, reliability, time-saving, and the like in the manufacturing processes. The connection/disconnection means that require manual work need complicated work and management under various specific fastening requirements. Consequently, the work efficiency may be impaired and human errors may be provoked. In particular, a change in impedance that occurs in the connection of coaxial cables with rated characteristic impedances may cause abnormal operations or malfunctions, and therefore transmission of power or signals needs matching of impedances at the connecting portion.
In addition, if conventional connectors are connected automatically with their center axes misaligned, such misalignment cannot be properly handled (cannot be corrected), and may thus cause breakage of the connectors or loose connection. If connectors are manually connected, misalignment of the center axes of the conductor portions of the connected connectors can be appropriately corrected on the spot. By contrast, if connectors are automatically connected, the connectors move linearly so that misalignment of the center axes of the conductor portions of the connected connectors results in such burdens as friction, loads, and stresses exerted on the conductor portions, and thus makes the connection more difficult. If such misaligned connectors are forcedly connected by use of a strong physical force, the connectors may be broken. Above all, the very existence of a mechanism that requires manual work prevents the connectors from being connected/disconnected automatically.
In recent years, manufacturing of semiconductors, flat-panel displays, and the like has required RF high power. Connectors that support the transmission of such high power as one exceeding 1 kw are currently connected to each other still by manual work because the need for the automatization of such connecting work has been scarcely felt.
Therefore, what is now demanded is a proposal for a coaxial connector including connectors easily connectable in a totally automated manner without requiring any manual work along with the electrical connection of coaxial cables supporting transmission of RF high power.